1. Field of the Invention
The present invention relates to a method for analyzing a protein or peptide and, more particularly, to a method for structural analysis of a posttranslational modified state of a protein or peptide by the use of no enzyme.
2. Description of the Related Art
Many proteins are variously modified after their translation. Of the modifications, phosphorylation is a principal posttranslational modification among the modifications which change physiological activities and enzymatic activities of various proteins and direct intracellular signal transmission or intracellular metabolic activity.
As the methods for detecting the phosphorylation of a protein, a method of using a radioisotope or a method of using an antibody and the like have been known (e.g., Proteome Variation Analysis by Isotope Labeling, pp. 111–122, by Oda, Detection of Phosphorylated Proteins, pp. 85–91, by Yanagida and Takahashi, Additional vol. of Experimental Medicine, Proteome Analytical Methods, 2000, Yodosha).
However, the method of using a radioisotope is defective since tyrosine phosphorylation cannot be discriminated from serine phosphorylation or threonine phosphorylation and also special facilities and an exclusive apparatus are necessary.
Moreover, the method of using an antibody has a defect that phosphorylated amounts between different proteins in a sample cannot be simply compared because, even when the same phosphorylated amino acid-recognizing antibody is used, bonding specificity of the antibody varies depending on the kind of protein containing a phosphorylated amino acid, and thus an enzyme immunoassay is required for determining the phosphorylation, which invites an increase in number of steps.
There has been no method which determines not only phosphorylation but also variously modified state of a protein or peptide such as sulfation or glycosylation at high accuracy and efficiency.